A fuse link is known from the German patent description DE102005063044 that is applicable as a fuse link installed inside the tank of an oil transformer or in the transformer bushing, inside the section immersed in transformer oil. The disclosed fuse link comprises a porcelain housing with a star-core with fuse-elements wound around it and a spring-type striker pin positioned along the axis of the star-core. The housing is filled with an arc-quenching medium and closed on both sides using external end caps, sealed with plugs one of which comprises a pass-through opening in which the striker pin is mounted. The star-core is held inside the fuse link by two star-core end caps designed as rings, each of them provided with a single tap whose function is to ensure electric contact between the star-core end cap and the external end cap of the fuse link. The spring-type striker pin is formed as an internal sleeve closed on its one side and slidably mounted inside an external sleeve that is positioned along the axis of the complete star-core. The internal sleeve is fixed in position along the axis of the external sleeve using a spring that is held in the stretched state by the wire of the internal striker pin so that when the wire is blown, the spring is released and the striker pin is actuated making the closed end of the internal sleeve move along the axis of the fuse link and pass through the outlet opening in the plug of the external end cap that is closed by a flat closing member designed as a ring, positioned on the external surface of the plug and slowing down the longitudinal movement of the external sleeve. The closing member is provided with a centrally located opening or cuts through which the internal sleeve of the striker pin passes. The plug is so designed that its internal flange is bent towards the inside of the fuse link, parallel to the axis of the fuse link which makes it possible to fix the external sleeve outside the flange on the internal side of the plug. The connection of the external sleeve with the plug is sealed using an adhesive sealant and this protects the internal space of the fuse link against penetration of external substances, such as transformer oil. To prevent the oil from entering the internal space of the fuse link, the contact points of the housing ends with the external end caps are sealed from the inside of the end caps and of the housing using a sealing compound. In addition, the sealing compound is applied between the external surfaces of the plugs and the internal surfaces of the end caps.
A disadvantage of the described solution lies in the need to ensure a high value of fit tolerance of the star-core to the star-core end caps. Additionally, in the described solution it is difficult to maintain the central position of the star-core relative to the external end cap of the fuse link due to unilateral support. In the described solution, the spring-type striker pin is fixed to the plug by welding and this requires additional operations during the installation of the striker pin inside the fuse link, and hence is relatively labour-intensive.
The Polish description of a utility model PL.66424Y1 discloses a fuse link comprising a porcelain housing, an insulating star-core with fuse-elements helically wound around it and connected to the electrically conductive first end cap and second end cap of the star-core. The star-core end caps are connected to external end caps of the fuse link that are mounted on the porcelain housing. The fuse link is provided with a spring-type striker pin with a needle unit, the striker pin being positioned along the axis of the fuse link between the first and the second external end caps. The external end caps have axially positioned pass-through openings one of which being closed using a flat closing member designed as a disc. The closing member is designed as a metal membrane permanently fixed to the flat surface of the inside part of the bottom of the second external end cap. The metal membrane is in direct contact with the bent portion of the flange of the striker pin sleeve on the outer side of the flange.
The described solutions fail to provide measures designed to simultaneously centre the star-core relative to the plugs, and the spring-type striker pin relative to one of the plugs.